The present invention is related to particulate material unloading devices of the type having a rotating auger powered to move about a central discharge sump in the floor of a storage bin and to engage and move particulate material toward the discharge sump.
Problems have been encountered in unloading large particulate storage bins. Such bins usually have a substantially horizontal floor and central discharge sumps. The discharge sumps are centrally located in the circular storage bins since any form of side unloading could cause serious structural problems with the walls of the bin.
The unloading problem has been solved to some degree by unloading auger mechanisms mounted within the bins. They are usually powered to move along the bin floor about a central vertical axis. The augers are powered to rotate as they move to engage particulate material and move it toward the sump discharge. One such device is illustrated by U.S. Pat. No. 3,647,094 granted to applicant, William J. Jackson on Mar. 7, 1972.
The device disclosed in U.S. Pat. No. 3,647,094 includes a single radially separable auger assembly extending from the center outlet sump and the vertical axis defined thereby. A tubular housing surrounds the auger with selectively operable doorways on a front side for guiding particulate material along the auger that rotates inside.
Such unit operates satisfactorily in unloading particulates such as grain from circular bins of up to forty feet high and one hundred feet in diameter. However, increasing unloader discharge demands and larger storage bins make a double auger assembly desirable.
Unloaders having diametrically opposed auger assemblies are not new. U.S. Pat. No. 1,274,548 granted Aug. 6, 1918 to W. A. Holnagel et al illustrates such an arrangement. Opposed auger unloaders have, in the past, been serviceable in individual specialized applications. However, modern equipment design has facilitated construction of hugh storage bins. Modern bins may receive various forms of loose particulate material in piles over eighty feet high, thus creating extremely high pressures at the bin floor.
Considerable power is required to rotate two augers about their axes and to drive them about the vertical axis of the outlet sump. Standard bevel gear drives used for powering prior opposed augers are too bulky, along with the required gear reduction mechanisms, to fit within the outlet sumps. Yet the bevel gear arrangement shown as early as U.S. Pat. No. 1,274,548 provides the desirable feature of driving the diametrically opposed augers in opposite directions about their respective axes. Counter auger rotation is more desirable than having two opposed augers that are rotated in the same direction with one auger having a right hand thread and the other auger having a left hand thread. Right and left hand augers, if turned about their axes in the same direction, will work unequally on opposite sides of the vertical rotational axis. One auger will have the tendency to "climb" the particulate pile while the other will rotate to effectively dig into the pile and move the material toward the outlet sump. Unequal discharge efficiency causes excessive strain at the center pivot point and results in low product output.
It becomes desirable then to provide an opposed auger unloader that has a unitary drive mechanism capable of delivering sufficient torque to oppositely rotate diametrically opposed augers while remaining sufficiently compact to fit easily within a standard outlet sump. It is also desirable to provide an unloader that has increased discharge capacity, even under heavily loaded conditions.